TopToolAIBMI Calculator for Kids and Teens
BMI calculator for kids and teens (children aged 2 to 19): a child's BMI cannot be judged on the adult table, because what is healthy changes every year as a child grows and is different for boys and girls. This calculator works out your child's BMI from weight and height and compares it with the CDC BMI-for-age growth charts for the same age and sex, giving a BMI percentile and a category: underweight (below the 5th percentile), healthy weight (5th to below 85th), overweight (85th to below 95th) or obesity (95th or above). It also shows the BMI values that mark each band at your child's age. For example, a 9-year-old boy who weighs 30 kg and is 135 cm tall has a BMI of 16.5, which is around the 56th percentile, in the healthy weight range, while a 12-year-old girl at 45 kg and 150 cm has a BMI of 20.0, around the 73rd percentile. BMI is a screening tool for children, not a diagnosis, so a growth spurt, puberty timing or build can all change it. If the result worries you, show it to your child's doctor, who can look at growth over time.
How to use BMI Calculator for Kids and Teens
Step-by-step guide to the boxes below. Open it only if you need help.
How to use BMI Calculator for Kids and Teens
Step-by-step guide to the boxes below. Open it only if you need help.
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1
Boy or girl Choose one
Choose the sex your child's growth chart is based on. Boys and girls grow differently, so the same BMI can fall in a different band for each.
Choose one: BoyGirl
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2
Age of child (years) Text
Type the age in years, and add .5 if the child is six months past a birthday, so 9 years 6 months is 9.5. The tool covers ages 2 to 19. For a child under 2, ask the doctor, who uses a different chart.
Example: 9
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3
Weight (kg) Text
Type your child's weight in kilograms. If the scale shows pounds, divide by 2.2 first (66 lb is about 30 kg). Weigh in light clothes, ideally at the same time of day.
Example: 70
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4
Height (cm) Text
Type your child's height in centimetres, not feet. Total inches x 2.54 gives centimetres, so 4 ft 3 in (51 in) is about 130 cm. Measure standing straight against a wall without shoes.
Example: 175
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5
Press “Calculate BMI”
Click the button under the boxes. If something is missing or not valid, a short message tells you which box to fix.
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6
Read your result
You get your child's BMI, the percentile it works out to for their age and sex, the category (underweight, healthy weight, overweight or obesity) and the BMI values that mark each band at that age. Change any box and try again to compare different numbers.
BMI Calculator for Kids and Teens FAQs
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